Generally speaking, a vehicle seat has a seat cushion, and a seat back mounted to the rear portion of the seat cushion. Each of the seat cushion and the seat back is mainly composed of a frame structure and a pad attached to the frame structure. The frame structure of the seat cushion has, for example, right and left panel portions and a front panel portion that are formed, for example, of plate materials (See JP 2007-212196 A).
However, since the front panel portion must be strong enough to withstand a shock at the time of collision or the like of the vehicle, it is necessary to perform drawing or bending on the plate material thereof to achieve an enhancement in strength. This involves a rather high cost. Therefore, there is a need in the art to provide a frame structure of a seat cushion for a vehicle seat which is of high strength and which can be formed at low cost.